The invention relates to a method of operating a welding machine comprising a frame, an electrode having a fixed position in the frame and an electrode which has been mounted in the frame so as to be movable with respect to said frame, which latter electrode is moved towards the fixed electrode to weld together components placed between the fixed and the movable electrode.
Such welding machines can be used, for example, in the manufacture of display tubes, more particularly in the manufacture of electron guns.
As regards the operation of the known welding machines, the movable electrode is customarily moved at a substantially constant rate from a starting position to the position suitable for welding; particularly if the devices are operated by man power, the rate of movement still is highly dependent on the operator. In this case, the components of the electron guns which are to be welded together, and which are placed on the fixed electrode, are contacted by the movable electrode at a comparatively high rate, causing undesirable vibrations in the electrodes and/or components when the movable electrode contacts said components, which may adversely affect the welds themselves and/or lead to the formation of undesirable welding spatters. However, electron guns having welding spatters and/or electron guns comprising components which are improperly welded together are unsuitable for use.
It is an object of the invention to maximally preclude the drawbacks occurring in the known method of welding together components.
In accordance with the invention, this object can be achieved in that during displacing the movable electrode from a starting position to a suitable position for welding, the movable electrode is moved more rapidly at the beginning of the displacement than at a location near the suitable welding position of the movable electrode.
By using the method in accordance with the invention, the movable electrode will contact the components to be welded together at a low rate, so that these components will be uniformly clamped between the movable electrode and the fixed electrode, and undesirable vibrations are precluded.
A further aspect of the invention relates to a welding machine comprising a frame, an electrode having a fixed position in the frame and an electrode which has been mounted in the frame so as to be movable with respect to said frame, which latter electrode can be moved by means of a man-power operated operating member in the direction of the fixed electrode by means of a transmission mechanism arranged between the operating member and the movable electrode.
In known welding machines of the above-mentioned type, the operating member is coupled to the movable electrode via a system of rods. As a result, the rate at which the electrode is displaced depends to a substantial degree on the person operating the welding machine, so that a constant operation of the machine cannot be ensured. A further drawback of the known welding machine resides in that the movable electrode contacts the welding components to be clamped between the fixed and the movable electrode at a comparatively high rate when it is moved towards the fixed electrode, which leads to undesirable vibrations at the location where said components are clamped, which adversely affects the welds and/or leads to the formation of welding spatters.
In accordance with the invention, the transmission mechanism is provided with a cam, which can be pivoted around a pivot pin from a starting position through a certain angle by means of the operating member to displace the movable electrode in the direction of the fixed electrode, which cam co-operates, during operation, with an adjusting member connected to the movable electrode, and the construction of the cam and the adjusting member co-operating with said cam being such that at the beginning of the pivotal motion of the cam for displacing the movable electrode in the direction of the fixed electrode, the adjusting member is displaced at a higher rate than during the pivotal motion of the cam through the last part of the angle through which the cam is pivotable around the pivot pin for displacing the movable electrode in the direction of the fixed electrode.
By means of the construction in accordance with the invention, it can be readily achieved that when the operating member is initially put into operation, the movable electrode is rapidly moved in the direction of the fixed electrode, while, in the last stage of the movement of the movable electrode, the rate of the movable electrode is reduced, so that the movable electrode reaches its final position, i.e. the position wherein the components to be welded together are clamped between the fixed and the movable electrode, at a low rate. As a result, undesirable vibrations which adversely affect welding are precluded.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.